Nowadays, many electronic devices are built by connecting together electrical components, ranging from a few electrical components in simple circuits to millions of them in complex circuits. Low power consumption has become one of the main issues in the electronics industry for many product areas such as cellular phones, biomedical implants, digital watches, calculators, tape players, portable computers, LCD driver circuits, in short, all types of portable and battery powered electronic devices.
For example, along with the recent increase in the popularity of portable equipment, the requests for large-scale integrated (LSI) devices performing battery operations are increasingly varied. Lowering the operating current (power supply current) to dramatically extend the operating time of battery operated systems is desirable.
Migrating to low operating voltages, denoted commonly as Vcc or Vdd, such as lower than 0.9 V is widely desired. Many traditional reference voltage circuits cannot meet this low voltage reference requirement. In some other reference circuits, such as the bandgap reference voltage generator shown in U.S. Pat. No. 4,628,248 by Birrittella et al, the current needed to activate the reference voltage generator results in high power consumption, due to use of bipolar transistors, e.g., IB and VBE. The quiescent current IQ may reach a very high value, i.e., the value of the current supply that is necessary to operate the shunt regulator may be too big. Typically, the value of the quiescent current used to correctly bias the reference voltage generator is at least several decades, such as 50-60 μA.
The bandgap reference voltage generator has the disadvantage of high power consumption. Thus, developing a type of shunt regulator other than the bandgap reference voltage generator is desired.